Internet communication formats are governed by the Internet Engineering Task Force (IETF). Internet protocol (IP) version four (IPv4) has provided the basic communication mechanism of the global Internet since its inception in the 1970s. As is known, communication on the Internet is comprised of Internet datagrams contained within network packets, each datagram having a datagram header and a datagram data area. The datagram header includes a source IP address and a destination IP address, which in IPv4 are each thirty-two bits in length. IPv4 addresses include a “netid” and a “hostid,” wherein the netid specifies a network and the hostid specifies a host, for example, an individual computer on the network.
There are a variety of ways in which the destination address can be used. For example, in “unicast” addressing, the destination address directs the network packet to one destination. Therefore, unicast is a point-to-point communication. IPv4 also supports “multicast” addressing for which a datagram is directed to a selected group of recipient hosts, rather than to one host. Therefore, multicast is a point to multiple point communication. Multicast is used, for example, in sending video and audio streams simultaneously to a group of recipients. IPv4 also supports “broadcast” addressing, for which a datagram is directed to all recipients connected to the network. The type of address, unicast, multicast, or broadcast, is identified by a few header bits near the beginning of the IPv4 packet header.
Internet protocol version six (IPv6) was generated by the IETF in the mid 1990's. The generation of IPv6 was necessitated by a variety of factors. Notably, the extraordinary proliferation of networks and devices connected to the Internet has resulted in an anticipated shortcoming of available Internet addresses under the IPv4 32-bit addressing technique. Therefore, among many other changes, IPv6 adopted a 128-bit addressing technique.
IPv6 retains unicast and multicast addressing and communication mechanisms associated with IPv4, but eliminates the broadcast capability. IPv6 also includes a new addressing referred to as “anycast.” Anycast is an addressing intended to communicate to a nearest one of a designated group of anycast members. Each of the group of anycast members has the same anycast address. However, a communication to the anycast group is sent only to the nearest anycast member, as is described in more detail below.
Request for Comments (RFC) 3513, or simply RFC3513, identifies the “anycast” address as an address that is assigned to more than one network interface, with the property that a data packet (i.e., a datagram) sent to an anycast address is routed to the “nearest” network interface having that address, according to a routing protocol's measure of distance. The nearest host can be determined in a variety of ways, for example, by a smallest number of router hops that a network packet must take to reach a selected member of the anycast group, or, for another example, by a smallest time delay associated with router port selections.
In one particular embodiment, an anycast group can include servers having redundant data and functionality. When a host communicates to the anycast group of servers, the nearest server receives the network packet and responds accordingly.
Currently (e.g., as specified in RFC3513), anycast addresses are allocated from the unicast address space. Thus, anycast addresses are syntactically indistinguishable from unicast addresses. When a unicast address is assigned to more than one anycast group member, thus turning it into an anycast address, the member to which the address is assigned must be explicitly configured to know that it should recognize the anycast address.
There are a variety of unresolved functional issues regarding anycast addressing. Some issues are discussed in an RFC1546. For example, a first network packet sent from a host to an anycast group of servers, using an anycast destination address, is received by one particular server of the anycast group of servers. However, if a second network packet is sent from the host to the anycast group of servers, using the anycast destination address, there is no guarantee that the second network packet will be received by the same server that received the first network packet. However, it may be desirable, in many instances, for the server that receives the second network packet and subsequent network packets to be the same server that received the first network packet. Issues such as this can be resolved in a variety of ways. For example, the server, upon receiving the first network packet, can respond with a unicast address, and the host and the server can thereafter communicate with unicast addressed packets.
Not only are there remaining functional issues regarding anycast addressing, but the specific bit-level structure of the anycast address itself has not yet been defined. Use of an anycast address has certain advantages, including but not limited to, shorter routing paths and resulting faster communications between a host and an anycast member. However, IPv6 does not specify the full intended use of anycast addressing, does not resolve all of its functional issues, and does not specify its bit-level structure.
It would, therefore, be desirable to overcome the aforesaid and other disadvantages, and to provide a system and method specifying the anycast bit-level address structure in a way capable of using anycast addressing, unicast addressing, and multicast addressing together on the same network.